The power company is set to decommission the San Onofre plant — one of two in California — after problems the could not be easily solved were found in one of its units.

About 20,000 people were asked to evacuate their homes near San Diego on Tuesday night, although the order was later lifted as firefighters got the upper hand on the blaze.

But on Wednesday, multiple fires erupted, including two at the Camp Pendleton base between Los Angeles and San Diego where a naval weapons station was evacuated, along with military housing and a school.

The fire charred brush along the nearby Interstate 5 freeway, which runs up and down the West Coast, at one point forcing its closure, although some lanes were later reopened.

In nearby Carlsbad, fires burned homes, downed power lines and forced evacuations of homeowners, as well as schoolchildren and tourists at the Legoland amusement park.

“The city of Carlsbad has done very well in clearing (brush around) those (threatened) homes, but when you have a wind-driven fire, it makes it very difficult,” said Cal Fire captain Mike Mohler.

“This is a very difficult firefight. This is an urban wildland firefight, so it is definitely more difficult than you would see in a more rural setting.”

California and other western US states are routinely hit with wildfires during the summer and fall, but blazes have occurred earlier in the year in recent times.

Southern California, including Los Angeles, has been bracing for record temperatures over 100 degrees Fahrenheit (38 degrees Celsius) this week, with authorities opening cooling centers for those otherwise unable to escape the heat.

A number of decades-old records for mid-May temperatures were broken Wednesday, including 96 degrees Farenheit at LAX airport and 99 degrees in downtown LA.

At Long Beach Airport, south of Los Angeles, a temperature of 101 degrees was recorded, beating the previous record of 93 degrees set in 1970.